The kidneys are a major target organ of hypertension. Prolonged hypertension induces various renal impairments, mainly through renovascular lesions. Among them, contraction of renal vessels and degenerative lesions of elastic fibers lead to further elevation of the blood pressure. It is generally believed that hypertension raises renal intraglomerular pressure, which overloads the glomeruli, stimulating fibrosis and enlargement of the mesangial region, which advances to hardening of the glomeruli. In diabetic nephropathy as well, elevation in intraglomerular pressure is followed by trace albuminuria, progressing to the sclerosis of the glomeruli. Eventually, renal functions decline, resulting in chronic renal failure requiring artificial dialysis therapy. In recent years, 20% of patients with end-stage renal failure who commence artificial dialysis have diabetic nephropathy as the underlying disease. The number of patients likely to receive artificial dialysis tends to increase year after year, posing a critical problem in the medical care system. At present, it is said that there are few ideal pharmaceutical therapies for chronic renal failure, and even that blood-pressure-lowering therapy may aggravate rather than improve renal failure.
Angiotensin II antagonistic compounds are known as a therapeutic drug for cardiovascular diseases, e.g., hypertension, cardiac diseases (heart enlargement, heart failure, myocardial infarction, etc.), apoplexy, nephritis, etc. (European Patent Official Gazette (EPO) 459136A). The mechanism of their action is considered to be based on inhibition of binding to the angiotensin II receptor of angiotensin II, which possesses intense vasoconstrictive action. EP 459136A.sub.1 describes the availability of angiotensin II antagonists in the treatment of nephropathy or nephritis.
Many data of clinical and experimental studies have been reported on the relation between renal diseases and hypertension. It is now established that the kidneys are directly or indirectly involved in the onset of hypertension, and also are apt to be affected by hypertension. However, hypertension in chronic glomerulonephritis has been poorly elucidated, particularly as to causative factors, effects of hypertension on the course of nephritis, and prophylactic effects of blood pressure lowering therapy.
Currently, nephritis is considered to be a clinical picture of different diseases with different entities. In accordance with the popularization of renal biopsy, renal diseases have been reviewed, resulting in their redefinition as a wide range of diseases characterized by proteinuria ("Shibata's Internal Medicine of the Kidneys," by Seiichi Shibata, Bunkodo, 1988). Glomerulonephritis, once regarded as a single disease, has been differentiated into glomerulonephritis, chronic pyelonephritis, IgA nephropathy, periarteritis nodosa, gout, diabetes, systemic lupus erythematosus (SLE), hepatic infarction, hereditary renal disease, amyloidosis, and Wegener's sarcoma.
Diabetes associated with hypertension facilitates cardiovascular impairment and/or other organ complications, greatly affecting life expectancy. Accordingly, it is important to control blood pressure within the normal range during treatment, along with the control of diabetes and the improvement or prevention of arteriosclerosis.